Reallocating storage in a dispersed storage network

ABSTRACT

A method for execution by a dispersed storage and task (DST) execution unit includes updating a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories. At least one encoded data slice is received for storage by the DST execution unit. A plurality of scores are generated corresponding to each of the plurality of memories, wherein each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories. One of the plurality of memories is selected based on the plurality of scores, and the at least one encoded data slice is stored in the selected memory.

BACKGROUND OF THE INVENTION

Technical Field of the Invention

Aspects of this invention relate generally to computer networks and more particularly to dispersed storage of data and distributed task processing of data.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, personal computers (PC), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on an Internet storage system. The Internet storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a distributed computing system in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present invention;

FIG. 3 is a diagram of an example of a distributed storage and task processing in accordance with the present invention;

FIG. 4A is a schematic block diagram of an embodiment of a decentralized agreement module in accordance with the present invention;

FIG. 4B is a flowchart illustrating an example of selecting the resource in accordance with the present invention;

FIG. 4C is a schematic block diagram of an embodiment of a dispersed storage network (DSN) in accordance with the present invention;

FIG. 4D is a flowchart illustrating an example of accessing a dispersed storage network (DSN) memory in accordance with the present invention;

FIG. 5 is schematic block diagram of an embodiment of a dispersed storage network (DSN) in accordance with the present invention; and

FIG. 6 is a flowchart illustrating an example of reallocating encoded data slice storage in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a distributed computing system 10 that includes a user device 12 and/or a user device 14, a distributed storage and/or task (DST) processing unit 16, a distributed storage and/or task network (DSTN) managing unit 18, a DST integrity processing unit 20, and a distributed storage and/or task network (DSTN) module 22. The components of the distributed computing system 10 are coupled via a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN). Hereafter, the distributed computing system 10 may be interchangeably referred to as a dispersed storage network (DSN).

The DSTN module 22 includes a plurality of distributed storage and/or task (DST) execution units 36 that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.). Each of the DST execution units is operable to store dispersed error encoded data and/or to execute, in a distributed manner, one or more tasks on data. The tasks may be a simple function (e.g., a mathematical function, a logic function, an identify function, a find function, a search engine function, a replace function, etc.), a complex function (e.g., compression, human and/or computer language translation, text-to-voice conversion, voice-to-text conversion, etc.), multiple simple and/or complex functions, one or more algorithms, one or more applications, etc. Hereafter, the DST execution unit may be interchangeably referred to as a storage unit and a set of DST execution units may be interchangeably referred to as a set of storage units.

Each of the user devices 12-14, the DST processing unit 16, the DSTN managing unit 18, and the DST integrity processing unit 20 include a computing core 26 and may be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a personal computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. User device 12 and DST processing unit 16 are configured to include a DST client module 34.

With respect to interfaces, each interface 30, 32, and 33 includes software and/or hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between user device 14 and the DST processing unit 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between user device 12 and the DSTN module 22 and between the DST processing unit 16 and the DSTN module 22. As yet another example, interface 33 supports a communication link for each of the DSTN managing unit 18 and DST integrity processing unit 20 to the network 24.

The distributed computing system 10 is operable to support dispersed storage (DS) error encoded data storage and retrieval, to support distributed task processing on received data, and/or to support distributed task processing on stored data. In general and with respect to DS error encoded data storage and retrieval, the distributed computing system 10 supports three primary operations: storage management, data storage and retrieval, and data storage integrity verification. In accordance with these three primary functions, data can be encoded (e.g., utilizing an information dispersal algorithm (IDA), utilizing a dispersed storage error encoding process), distributedly stored in physically different locations, and subsequently retrieved in a reliable and secure manner. Hereafter, distributedly stored may be interchangeably referred to as dispersed stored. Such a system is tolerant of a significant number of failures (e.g., up to a failure level, which may be greater than or equal to a pillar width (e.g., an IDA width of the IDA) minus a decode threshold minus one) that may result from individual storage device (e.g., DST execution unit 36) failures and/or network equipment failures without loss of data and without the need for a redundant or backup copy. Further, the distributed computing system 10 allows the data to be stored for an indefinite period of time without data loss and does so in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

The second primary function (i.e., distributed data storage and retrieval) begins and ends with a user device 12-14. For instance, if a second type of user device 14 has data 40 to store in the DSTN module 22, it sends the data 40 to the DST processing unit 16 via its interface 30. The interface 30 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). In addition, the interface 30 may attach a user identification code (ID) to the data 40.

To support storage management, the DSTN managing unit 18 performs DS management services. One such DS management service includes the DSTN managing unit 18 establishing distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for a user device 12-14 individually or as part of a group of user devices. For example, the DSTN managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within memory of the DSTN module 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The DSTN managing unit 18 may facilitate storage of DS error encoding parameters for each vault of a plurality of vaults by updating registry information for the distributed computing system 10. The facilitating includes storing updated system registry information in one or more of the DSTN module 22, the user device 12, the DST processing unit 16, and the DST integrity processing unit 20.

The DS error encoding parameters (e.g., or dispersed storage error coding parameters for encoding and decoding) include data segmenting information (e.g., how many segments data (e.g., a file, a group of files, a data block, etc.) is divided into), segment security information (e.g., per segment encryption, compression, integrity checksum, etc.), error coding information (e.g., pillar/IDA width, decode threshold, read threshold, write threshold, etc.), slicing information (e.g., the number of encoded data slices that will be created for each data segment); and slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

The DSTN managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSTN module 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The DSTN managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the DSTN managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate a per-access billing information. In another instance, the DSTN managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount billing information.

Another DS management service includes the DSTN managing unit 18 performing network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system 10, and/or establishing authentication credentials for DST execution units 36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the system 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the system 10.

To support data storage integrity verification within the distributed computing system 10, the DST integrity processing unit 20 performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the DST integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSTN module 22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in memory of the DSTN module 22. Note that the DST integrity processing unit 20 may be a separate unit as shown, it may be included in the DSTN module 22, it may be included in the DST processing unit 16, and/or distributed among the DST execution units 36.

Each slice name is unique to a corresponding encoded data slice and includes multiple fields associated with the overall namespace of the DSN. For example, the fields may include a pillar number/pillar index, a vault identifier, an object number uniquely associated with a particular file for storage, and a data segment identifier of a plurality of data segments, where the particular file is divided into the plurality of data segments. For example, each slice name of a set of slice names corresponding to a set of encoded data slices that has been dispersed storage error encoded from a common data segment varies only by entries of the pillar number field as each share a common vault identifier, a common object number, and a common data segment identifier.

To support distributed task processing on received data, the distributed computing system 10 has two primary operations: DST (distributed storage and/or task processing) management and DST execution on received data. With respect to the storage portion of the DST management, the DSTN managing unit 18 functions as previously described. With respect to the tasking processing of the DST management, the DSTN managing unit 18 performs distributed task processing (DTP) management services. One such DTP management service includes the DSTN managing unit 18 establishing DTP parameters (e.g., user-vault affiliation information, billing information, user-task information, etc.) for a user device 12-14 individually or as part of a group of user devices.

Another DTP management service includes the DSTN managing unit 18 performing DTP network operations, network administration (which is essentially the same as described above), and/or network maintenance (which is essentially the same as described above). Network operations include, but are not limited to, authenticating user task processing requests (e.g., valid request, valid user, etc.), authenticating results and/or partial results, establishing DTP authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system, and/or establishing DTP authentication credentials for DST execution units.

To support distributed task processing on stored data, the distributed computing system 10 has two primary operations: DST (distributed storage and/or task) management and DST execution on stored data. With respect to the DST execution on stored data, if the second type of user device 14 has a task request 38 for execution by the DSTN module 22, it sends the task request 38 to the DST processing unit 16 via its interface 30. With respect to the DST management, it is substantially similar to the DST management to support distributed task processing on received data.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (IO) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSTN interface module 76.

The DSTN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSTN interface module 76 and/or the network interface module 70 may function as the interface 30 of the user device 14 of FIG. 1. Further note that the IO device interface module 62 and/or the memory interface modules may be collectively or individually referred to as IO ports.

FIG. 3 is a diagram of an example of the distributed computing system performing a distributed storage and task processing operation. The distributed computing system includes a DST (distributed storage and/or task) client module 34 (which may be in user device 14 and/or in DST processing unit 16 of FIG. 1), a network 24, a plurality of DST execution units 1-n that includes two or more DST execution units 36 of FIG. 1 (which form at least a portion of DSTN module 22 of FIG. 1), a DST managing module (not shown), and a DST integrity verification module (not shown). The DST client module 34 includes an outbound DST processing section 80 and an inbound DST processing section 82. Each of the DST execution units 1-n includes a controller 86, a processing module 84, memory 88, a DT (distributed task) execution module 90, and a DST client module 34.

In an example of operation, the DST client module 34 receives data 92 and one or more tasks 94 to be performed upon the data 92. The data 92 can be of any size and of any content, where, due to the size (e.g., greater than a few Terabytes), the content (e.g., secure data, etc.), and/or task(s) (e.g., MIPS intensive), distributed processing of the task(s) on the data is desired. For example, the data 92 can be one or more digital books, a copy of a company's emails, a large-scale Internet search, a video security file, one or more entertainment video files (e.g., television programs, movies, etc.), data files, and/or any other large amount of data (e.g., greater than a few Terabytes).

Within the DST client module 34, the outbound DST processing section 80 receives the data 92 and the task(s) 94. The outbound DST processing section 80 processes the data 92 to produce slice groupings 96. As an example of such processing, the outbound DST processing section 80 partitions the data 92 into a plurality of data partitions. For each data partition, the outbound DST processing section 80 dispersed storage (DS) error can encode the data partition to produce encoded data slices and groups the encoded data slices into a slice grouping 96. In addition, the outbound DST processing section 80 can partition the task 94 into partial tasks 98, where the number of partial tasks 98 may correspond to the number of slice groupings 96.

The outbound DST processing section 80 can then send, via the network 24, the slice groupings 96 and the partial tasks 98 to the DST execution units 1-n of the DSTN module 22 of FIG. 1. For example, the outbound DST processing section 80 sends slice group 1 and partial task 1 to DST execution unit 1. As another example, the outbound DST processing section 80 can send slice group #n and partial task #n to DST execution unit #n.

Each DST execution unit performs its partial task 98 upon its slice group 96 to produce partial results 102. For example, DST execution unit 1 performs partial task 1 on slice group 1 to produce a partial result 1, for results. As a more specific example, slice group 1 corresponds to a data partition of a series of digital books and the partial task #1 corresponds to searching for specific phrases, recording where the phrase is found, and establishing a phrase count. In this more specific example, the partial result 1 includes information as to where the phrase was found and includes the phrase count.

Upon completion of generating their respective partial results 102, the DST execution units can send, via the network 24, their partial results 102 to the inbound DST processing section 82 of the DST client module 34. The inbound DST processing section 82 can process the received partial results 102 to produce a result 104. Continuing with the specific example of the preceding paragraph, the inbound DST processing section 82 can combine the phrase count from each of the DST execution units 36 to produce a total phrase count. In addition, the inbound DST processing section 82 can combine the ‘where the phrase was found’ information from each of the DST execution units 36 within their respective data partitions to produce ‘where the phrase was found’ information for the series of digital books.

In another example of operation, the DST client module 34 requests retrieval of stored data within the memory of the DST execution units 36 (e.g., memory of the DSTN module). In this example, the task 94 is retrieve data stored in the memory of the DSTN module. Accordingly, the outbound DST processing section 80 converts the task 94 into a plurality of partial tasks 98 and sends the partial tasks 98 to the respective DST execution units 1-n.

In response to the partial task 98 of retrieving stored data, a DST execution unit 36 identifies the corresponding encoded data slices 100 and retrieves them. For example, DST execution unit 1 receives partial task 1 and retrieves, in response thereto, retrieved slices 1. The DST execution units 36 send their respective retrieved slices 100 to the inbound DST processing section 82 via the network 24.

The inbound DST processing section 82 converts the retrieved slices 100 into data 92. For example, the inbound DST processing section 82 de-groups the retrieved slices 100 to produce encoded slices per data partition. The inbound DST processing section 82 can then DS error decodes the encoded slices per data partition to produce data partitions. The inbound DST processing section 82 can de-partition the data partitions to recapture the data 92.

FIG. 4A is a schematic block diagram of an embodiment of a decentralized agreement module 350 that includes a set of deterministic functions 1-N, a set of normalizing functions 1-N, a set of scoring functions 1-N, and a ranking function 352. The deterministic function, the normalizing function, the scoring function, and/or the ranking function 352, can be implemented utilizing the processing module 84 of FIG. 3. The decentralized agreement module 350 may be implemented utilizing any module and/or unit of a dispersed storage network (DSN). For example, the decentralized agreement module is implemented utilizing the distributed storage and task (DST) client module 34 of FIG. 1 via a processing system that includes at least one processor and memory that stores instruction that configure the processor or processors to perform the functions described herein.

The decentralized agreement module 350 functions to receive a ranked scoring information request 354 and to generate ranked scoring information 358 based on the ranked scoring information request 354 and/or other information. The ranked scoring information request 354 can include an asset identifier (ID) 356 of an asset associated with the request, an asset type indicator, one or more location identifiers of locations associated with the DSN, one or more corresponding location weights a requesting entity ID and/or other information. The asset can include any portion of data associated with the DSN including one or more asset types including a data object, a data record, an encoded data slice, a data segment, a set of encoded data slices, a plurality of sets of encoded data slices and/or other data. As such, the asset ID 356 of the asset can include a data name, a data record identifier, a source name, a slice name, a plurality of sets of slice names and/or other information.

Each location of the DSN includes an aspect of a DSN resource. Examples of locations include a storage unit, a memory device of the storage unit, a site, a storage pool of storage units, a pillar index associated with each encoded data slice of a set of encoded data slices generated by an information dispersal algorithm (IDA), a DST client module 34 of FIG. 1, a DST processing unit 16 of FIG. 1, a DST integrity processing unit 20 of FIG. 1, a DSTN managing unit 18 of FIG. 1, a user device 12 of FIG. 1, and a user device 14 of FIG. 1.

Each location is associated with a location weight based on a resource prioritization of utilization scheme and/or a physical configuration of the DSN. The location weight can include an arbitrary bias which adjusts a proportion of selections to an associated location such that a probability that an asset will be mapped to that location is equal to the location weight divided by a sum of all location weights for all locations of comparison. For example, each storage pool of a plurality of storage pools can be associated with a location weight based on storage capacity. For instance, storage pools with more storage capacity can be associated with higher location weights than others. The other information may include a set of location identifiers and a set of location weights associated with the set of location identifiers. For example, the other information can include location identifiers and location weights associated with a set of memory devices of a storage unit when the requesting entity utilizes the decentralized agreement module 350 to produce ranked scoring information 358 with regards to selection of a memory device of the set of memory devices for accessing a particular encoded data slice (e.g., where the asset ID includes a slice name of the particular encoded data slice).

The decentralized agreement module 350 outputs substantially identical ranked scoring information for each ranked scoring information request that includes substantially identical content of the ranked scoring information request. For example, a first requesting entity issues a first ranked scoring information request to the decentralized agreement module 350 and receives first ranked scoring information. A second requesting entity issues a second ranked scoring information request to the decentralized agreement module and receives second ranked scoring information. The second ranked scoring information is substantially the same as the first ranked scoring information when the second ranked scoring information request is substantially the same as the first ranked scoring information request.

As such, two or more requesting entities may utilize the decentralized agreement module 350 to determine substantially identical ranked scoring information. As a specific example, the first requesting entity selects a first storage pool of a plurality of storage pools for storing a set of encoded data slices utilizing the decentralized agreement module 350 and the second requesting entity identifies the first storage pool of the plurality of storage pools for retrieving the set of encoded data slices utilizing the decentralized agreement module 350.

In an example of operation, the decentralized agreement module 350 receives the ranked scoring information request 354. Each deterministic function performs a deterministic function on a combination and/or concatenation (e.g., add, append, interleave) of the asset ID 356 of the ranked scoring information request 354 and an associated location ID of the set of location IDs to produce an interim result. The deterministic function can include a hashing function, a hash-based message authentication code function, a mask generating function, a cyclic redundancy code function, hashing module of a number of locations, consistent hashing, rendezvous hashing, a sponge function and/or some other function. As a specific example, deterministic function 2 appends a location ID 2 of a storage pool 2 to a source name as the asset ID to produce a combined value and performs the mask generating function on the combined value to produce interim result 2.

With a set of interim results 1-N, each normalizing function performs a normalizing function on a corresponding interim result to produce a corresponding normalized interim result. The performing of the normalizing function can include dividing the interim result by a number of possible permutations of the output of the deterministic function to produce the normalized interim result. For example, normalizing function 2 performs the normalizing function on the interim result 2 to produce a normalized interim result 2.

With a set of normalized interim results 1-N, each scoring function performs a scoring function on a corresponding normalized interim result to produce a corresponding score. Performance of the scoring function can include dividing an associated location weight by a negative log of the normalized interim result. For example, scoring function 2 divides location weight 2 of the storage pool 2 (e.g., associated with location ID 2) by a negative log of the normalized interim result 2 to produce a score 2.

With a set of scores 1-N, the ranking function 352 performs a ranking function on the set of scores 1-N to generate the ranked scoring information 358. The ranking function can include rank ordering each score with other scores of the set of scores 1-N, where a highest score is ranked first or highest. As such, a location associated with the highest score may be considered a highest priority location for resource utilization (e.g., accessing, storing, retrieving, etc. the given asset of the request). Having generated the ranked scoring information 358, the decentralized agreement module 350 outputs the ranked scoring information 358 to the requesting entity.

FIG. 4B is a flowchart illustrating an example of selecting a resource. In step 360, a processing module (e.g., of a decentralized agreement module) receives a ranked scoring information request from a requesting entity with regards to a set of candidate resources. For each candidate resource, the method continues at step 362 where the processing module performs a deterministic function on a location identifier (ID) of the candidate resource and an asset ID of the ranked scoring information request to produce an interim result. As a specific example, the processing module combines the asset ID and the location ID of the candidate resource to produce a combined value and performs a hashing function on the combined value to produce the interim result.

For each interim result, the method continues at step 364 where the processing module performs a normalizing function on the interim result to produce a normalized interim result. As a specific example, the processing module obtains a permutation value associated with the deterministic function (e.g., maximum number of permutations of output of the deterministic function) and divides the interim result by the permutation value to produce the normalized interim result (e.g., with a value between 0 and 1).

For each normalized interim result, the method continues at step 366 where the processing module performs a scoring function on the normalized interim result utilizing a location weight associated with the candidate resource associated with the interim result to produce a score of a set of scores. As a specific example, the processing module divides the location weight by a negative log of the normalized interim result to produce the score.

The method continues at step 368 where the processing module rank orders the set of scores to produce ranked scoring information (e.g., ranking a highest value first). The method continues at step 370 where the processing module outputs the ranked scoring information to the requesting entity. The requesting entity may utilize the ranked scoring information to select one location of a plurality of locations.

FIG. 4C is a schematic block diagram of an embodiment of a dispersed storage network (DSN) that includes the distributed storage and task (DST) processing unit 16 of FIG. 1, the network 24 of FIG. 1, and the distributed storage and task network (DSTN) module 22 of FIG. 1. Hereafter, the DSTN module 22 may be interchangeably referred to as a DSN memory. The DST processing unit 16 includes a decentralized agreement module 380 and the DST client module 34 of FIG. 1. The decentralized agreement module 380 be implemented utilizing the decentralized agreement module 350 of FIG. 5A. The DSTN module 22 includes a plurality of DST execution (EX) unit pools 1-P. Each DST execution unit pool includes one or more sites 1-S. Each site includes one or more DST execution units 1-N. Each DST execution unit may be associated with at least one pillar of N pillars associated with an information dispersal algorithm (IDA), where a data segment is dispersed storage error encoded using the IDA to produce one or more sets of encoded data slices, and where each set includes N encoded data slices and like encoded data slices (e.g., slice 3's) of two or more sets of encoded data slices are included in a common pillar (e.g., pillar 3). Each site may not include every pillar and a given pillar may be implemented at more than one site. Each DST execution unit includes a plurality of memories 1-M. Each DST execution unit may be implemented utilizing the DST execution unit 36 of FIG. 1. Hereafter, a DST execution unit may be referred to interchangeably as a storage unit and a set of DST execution units may be interchangeably referred to as a set of storage units and/or as a storage unit set.

The DSN functions to receive data access requests 382, select resources of at least one DST execution unit pool for data access, utilize the selected DST execution unit pool for the data access, and issue a data access response 392 based on the data access. The selection of the resources can include utilizing a decentralized agreement function of the decentralized agreement module 380, where a plurality of locations are ranked against each other. The selection may also include selecting one storage pool of the plurality of storage pools, selecting DST execution units at various sites of the plurality of sites, selecting a memory of the plurality of memories for each DST execution unit, and selecting combinations of memories, DST execution units, sites, pillars, and/or storage pools.

In an example of operation, the DST client module 34 receives the data access request 382 from a requesting entity, where the data access request 382 includes a store data request, a retrieve data request, a delete data request, a data name, and/or a requesting entity identifier (ID). Having received the data access request 382, the DST client module 34 determines a DSN address associated with the data access request. The DSN address includes a source name (e.g., including a vault ID and an object number associated with the data name), a data segment ID, a set of slice names, and/or a plurality of sets of slice names. Determining the DSN address can include generating the DSN address (e.g., for the store data request) or retrieving the DSN address (e.g., from a DSN directory, from a dispersed hierarchical index) based on the data name (e.g., for the retrieve data request).

Having determined the DSN address, the DST client module 34 selects a plurality of resource levels (e.g., DST EX unit pool, site, DST execution unit, pillar, memory) associated with the DSTN module 22. The selection of the resource levels may be based on the data name, the requesting entity ID, a predetermination, a lookup, a DSN performance indicator, interpreting an error message and/or other information. For example, the DST client module 34 selects the DST execution unit pool as a first resource level and a set of memory devices of a plurality of memory devices as a second resource level based on a system registry lookup for a vault associated with the requesting entity.

Having selected the plurality of resource levels, the DST client module 34, for each resource level, issues a ranked scoring information request 384 to the decentralized agreement module 380 utilizing the DSN address as an asset ID. The decentralized agreement module 380 performs the decentralized agreement function based on the asset ID (e.g., the DSN address), identifiers of locations of the selected resource levels, and location weights of the locations to generate ranked scoring information 386.

For each resource level, the DST client module 34 receives corresponding ranked scoring information 386. Having received the ranked scoring information 386, the DST client module 34 identifies one or more resources associated with the resource level based on the rank scoring information 386. For example, the DST client module 34 identifies a DST execution unit pool associated with a highest score and identifies a set of memory devices within DST execution units of the identified DST execution unit pool with a highest score.

Having identified the one or more resources, the DST client module 34 accesses the DSTN module 22 based on the identified one or more resources associated with each resource level. For example, the DST client module 34 issues resource access requests 388 (e.g., write slice requests when storing data, read slice requests when recovering data) to the identified DST execution unit pool, where the resource access requests 388 further identify the identified set of memory devices. Having accessed the DSTN module 22, the DST client module 34 receives resource access responses 390 (e.g., write slice responses, read slice responses). The DST client module 34 issues the data access response 392 based on the received resource access responses 390. For example, the DST client module 34 decodes received encoded data slices to reproduce data and generates the data access response 392 to include the reproduced data.

FIG. 4D is a flowchart illustrating an example of accessing a dispersed storage network (DSN) memory. In step 394, a processing module (e.g., of a distributed storage and task (DST) client module) receives a data access request from a requesting entity. The data access request can include a storage request, a retrieval request, a requesting entity identifier, a data identifier (ID) and/or other information. The method continues at step 396 where the processing module determines a DSN address associated with the data access request. For example, the processing module generates the DSN address for the storage request. As another example, the processing module performs a lookup for the retrieval request based on the data identifier.

The method continues at step 398 where the processing module selects a plurality of resource levels associated with the DSN memory. The selection, for example may be based on a predetermination, a range of weights associated with available resources, a resource performance level, and/or a resource performance requirement level. For each resource level, the method continues at step 400 where the processing module determines ranked scoring information. For example, the processing module issues a ranked scoring information request to a decentralized agreement module based on the DSN address and receives corresponding ranked scoring information for the resource level, where the decentralized agreement module performs a decentralized agreement protocol function on the DSN address using the associated resource identifiers and resource weights for the resource level to produce the ranked scoring information for the resource level.

For each resource level, the method continues at step 402 where the processing module selects one or more resources associated with the resource level based on the ranked scoring information. For example, the processing module selects a resource associated with a highest score when one resource is required. As another example, the processing module selects a plurality of resources associated with highest scores when a plurality of resources are required.

The method continues at step 404 where the processing module accesses the DSN memory utilizing the selected one or more resources for each of the plurality of resource levels. For example, the processing module identifies network addressing information based on the selected resources including one or more of a storage unit Internet protocol address and a memory device identifier, generates a set of encoded data slice access requests based on the data access request and the DSN address, and sends the set of encoded data slice access requests to the DSN memory utilizing the identified network addressing information.

The method continues at step 406 where the processing module issues a data access response to the requesting entity based on one or more resource access responses from the DSN memory. For example, the processing module issues a data storage status indicator when storing data. As another example, the processing module generates the data access response to include recovered data when retrieving data.

FIG. 5 is a schematic block diagram of another embodiment of a dispersed storage network (DSN) that includes a set of distributed storage and task (DST) execution (EX) units 1-n, the network 24 of FIG. 1, and the DST processing unit 16 of FIG. 1. Each DST execution unit includes a decentralized agreement module, the DST client module 34 of FIG. 1, and a plurality of memories 1-M. The decentralized agreement module may be implemented utilizing the decentralized agreement module 350 of FIG. 4A. Each memory may be implemented utilizing the memory 88 of FIG. 3. Each DST execution unit may be implemented utilizing the DST execution unit 36 of FIG. 1. Hereafter, the set of DST execution units may be interchangeably referred to as a set of storage units and each DST execution unit may be interchangeably referred to as a storage unit. The DST processing unit 16 includes the DST client module 34 of FIG. 1. The DSN functions to reallocate encoded data slice storage.

In many memory devices, there is some space reserved for handling internal errors that result in a decrease of that device's capacity. For example, Hard Drives with reserved bad blocks to take over from failed blocks elsewhere on the platter, or SSDs with whole redundant banks of memory. Normally, when this spare capacity is exhausted, the device fails irrecoverably. As an alternative, if the usable capacity of the memory device were to merely continue to shrink as more and more failures occurred, this would extend the usable life and utility of the component, which is still non-zero, despite having less capacity. Yet in a DST execution unit of many memory devices, having some memory devices of lesser capacity can be problematic: if one memory device reaches 100% before the others, then some writes to that DST execution unit will fail with out of space errors. To avoid this condition, while maintaining the capacity to operate with degraded/reduced capacity memory devices, a Decentralized Agreement Protocol (DAP) may be used to effectively “shrink” the capacity of a memory device within a DST execution unit, such that utilization across all memory devices in a DST execution unit remains equal. By using a DAP to determine on which memory device to store a slice, and by using a Resource Map that indicates the relative remaining healthy storage capacities of each memory device, the placement of slices can be weighted according to the storage capacity of each memory device. When a degradation occurs that causes the usable capacity of a memory device to shrink, e.g. when a zone in an SMR drive, a platter or read head associated with a platter in a hard drive, a NAND array in an SSD fails, or any similar fault, the DST execution unit may determine the new usable capacity of the memory device, then update the resource map, then reapply the DAP to the slices stored on that memory device. Since the device's capacity is reduced, the DAP will reallocate those slices to other memory devices in the DST execution unit, eventually achieving equalized utilization

In an embodiment, a processing system of a dispersed storage and task (DST) execution unit comprises at least one processor and a memory that stores operational instructions, that when executed by the at least one processor causes the processing system to update a plurality of weighting factors corresponding to each of a plurality of memories 1-M in response to an indication of a change in memory capacity of one of the plurality of memories. At least one encoded data slice is received for storage by DST execution unit. A plurality of scores are generated corresponding to each of the plurality of memories, where each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories. One of the plurality of memories is selected based on the plurality of scores, and the at least one encoded data slice is stored in the selected one of the plurality of memories.

In various embodiments of the processing system of the DST execution unit, the indication of the change of the memory capacity is generated based on interpreting an error message.

In various embodiments of the processing system of the DST execution unit, execution of the operational instructions by the at least one processor further causes the processing system to perform a memory test on the plurality of memories, and the indication of the change of memory capacity is generated based on comparing a result of the memory test to a previous result corresponding to a previous memory test. The indication of the change of the memory capacity can be generated based on one of: a failure or removal of a memory block of the one of the plurality of memories. The plurality of weighting factors can be updated in response to an indication that the change in memory capacity is greater than a predefined threshold.

In various embodiments of the processing system of the DST execution unit, the selected one of the plurality of memories is determined based on the corresponding one of the plurality of memories with the highest corresponding score. Each of the plurality of scores can be further generated based on an attribute of the received encoded slice.

The indication of a change in the memory capacity can indicate a lowered memory capacity of the one of the plurality of memories, and the plurality of weighting factors can be updated by decreasing a weighting factor of the plurality of weighting factors corresponding to the one of the plurality of memories with the lowered memory capacity, and increasing remaining ones of the weighting factors of remaining memories of the plurality of memories.

In various embodiments of the processing system of the DST execution unit, the decrease of the weighting factor of the corresponding one of the plurality of memories with the lowered memory capacity can be proportional to a degree of change in the memory capacity, and remaining ones of the plurality of weighting factors corresponding to the remaining memories are increased based on the decrease in the weighting factor of the one of the plurality of memories with the lowered memory capacity. The plurality of weighting factors can be updated in response to an indication that at least one second encoded data slice has been either written to or deleted from the one of the plurality of memories.

In various embodiments, a storage unit determines that a memory capacity level of a memory of the plurality of memories of the storage unit has changed. For example, the memory capacity level may change as a result of a memory block failing, a memory block being taken out of service, or adding a memory block or other memory capacity to the memory. The determining that the memory capacity level of a memory has changed may include interpreting an error message, interpreting a memory test result, comparing a test result to a previous test result and/or accessing system registry information. For example, the DST execution unit 1 indicates that the memory capacity level of memory 2 of the DST execution unit 1 has changed when a memory block of the memory 2 has failed and has been taken out of service. The storage unit can also routinely perform scheduled memory tests to determine if the memory capacity has changed.

When the memory capacity level of the memory has changed, the storage unit updates weighting factors of the plurality of memories of the storage unit in accordance with a degree of the change in the memory capacity level. For example, when the memory capacity is lowered, the updating can include lowering a weighting factor of the memory in accordance with the degree of lowering, and raising weighting factors of remaining memories (e.g., memory 1, memories 3-M) of the plurality of memories based on the lowering of the weighting factor in the memory (e.g., to proportionately spread out the overall weighting). In various embodiments, the storage unit measures the change in memory capacity and only updates weighting factors if the change in memory is greater than a certain threshold.

In various embodiments, the memory capacity level is determined based on the remaining capacity of the memory. Determining that a memory capacity level of a memory has changed can also include determining if the amount of remaining, available memory has changed. For example, a change in memory capacity can determined by an indication that a large file was recently added or removed from a memory block in the memory. In various embodiments, the storage unit actively tracks and records when encoded data slices are written or removed from memory, and can store a current value, updated with each added or deleted slice, indicating the amount of remaining memory. In various embodiments, any addition or deletion of a data slice will trigger the storage unit to update the weighting factors accordingly. In other embodiments, the storage unit will monitor when data slices are written or removed and/or monitor a current value indicating the amount of memory remaining, and only update the weighing factors when the change in remaining memory capacity is above a certain threshold, or when the number of data slices added or deleted is above a certain threshold.

In various embodiments, when the storage unit receives encoded data slice for storage and receives a corresponding slice name, for each memory of the plurality of memories, the storage unit performs a distributed agreement protocol function on a slice name of the received encoded data slice using an identifier of the memory and an updated weighting factor of the memory to produce a score of a plurality of scores. The distributed agreement protocol function can be performed on a slice name, slice identifier, identifier corresponding to the source of the slice, and/or another identifier associated with the slice. For example, the DST processing unit 16 issues a set of encoded data slices 1-n, the distributed agreement module of the DST execution unit 1 performs the distributed agreement protocol function on a slice name of received encoded data slice 1 using the identifier of the memory (e.g., one at a time from 1-M) and the updated weighting factor of the memory to produce the plurality of scores. In various embodiments, the distributed agreement protocol function can be performed by the decentralized agreement module 350 previously described and presented in FIG. 4A.

Having produced the plurality of scores, the storage unit facilitates storage of the received encoded data slice in a memory associated with a highest score of the plurality of scores. For example, the DST client module 34 of the DST execution unit 1 identifies highest score, identifies the memory (e.g., memory 6) associated with a highest score, and stores the received encoded data slice 1 in the identified memory.

FIG. 6 is a flowchart illustrating an example of reallocating encoded data slice storage. In particular, a method is presented for use in conjunction with one or more functions and features described in conjunction with FIGS. 1-5 for execution by a dispersed storage and task (DST) execution unit that includes a processor or via another processing system of a dispersed storage network that includes at least one processor and memory that stores instruction that configure the processor or processors to perform the steps described below. Step 602 includes updating a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories. Step 604 includes receiving at least one encoded data slice for storage by the DST execution unit. Step 606 includes generating a plurality of scores corresponding to each of the plurality of memories, where each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories. Step 608 includes selecting one of the plurality of memories based on the plurality of scores. Step 610 includes storing the at least one encoded data slice in the selected one of the plurality of memories.

In various embodiments, the indication of the change of the memory capacity is generated based on interpreting an error message. The method can further include performing a memory test on the plurality of memories and, the indication of the change of memory capacity is generated based on comparing a result of the memory test to a previous result corresponding to a previous memory test. The indication of the change of the memory capacity can be generated based on one of: a failure or removal of a memory block of the one of the plurality of memories.

The plurality of weighting factors can be updated in response to an indication that the change in memory capacity is greater than a predefined threshold. The selected one of the plurality of memories can be determined based on the corresponding one of the plurality of memories with the highest corresponding score. Each of the plurality of scores can be further generated based on an attribute of the received encoded slice.

In various embodiments, the indication of a change in the memory capacity indicates a lowered memory capacity of the one of the plurality of memories, and the plurality of weighting factors can be updated by decreasing a weighting factor of the plurality of weighting factors corresponding to the one of the plurality of memories with the lowered memory capacity, and increasing remaining ones of the weighting factors of remaining memories of the plurality of memories. The decrease of the weighting factor of the corresponding one of the plurality of memories with the lowered memory capacity can be proportional to a degree of change in the memory capacity, and remaining ones of the plurality of weighting factors corresponding to the remaining memories can be increased based on the decrease in the weighting factor of the one of the plurality of memories with the lowered memory capacity. In addition, the plurality of weighting factors can be updated in response to an indication that at least one second encoded data slice has been either written to or deleted from the one of the plurality of memories.

In an embodiment, a non-transitory computer readable storage medium comprises at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to update a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories, receive at least one encoded data slice for storage, generate a plurality of scores corresponding to each of the plurality of memories, where each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories, select one of the plurality of memories based on the plurality of scores, and store the at least one encoded data slice in the selected one of the plurality of memories.

The method described above in conjunction with the computing device and the storage units can alternatively be performed by other modules of the dispersed storage network or by other devices. For example, any combination of a first module, a second module, a third module, a fourth module, etc. of the computing device and the storage units may perform the method described above. In addition, at least one memory section (e.g., a first memory section, a second memory section, a third memory section, a fourth memory section, a fifth memory section, a sixth memory section, etc. of a non-transitory computer readable storage medium) that stores operational instructions can, when executed by one or more processing modules of one or more computing devices and/or by the storage units of the dispersed storage network (DSN), cause the one or more computing devices and/or the storage units to perform any or all of the method steps described above.

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1.

As may also be used herein, the terms “processing module”, “processing circuit”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

The present invention has been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof

In addition, a flow diagram may include a “start” and/or “continue” indication. The “start” and “continue” indications reflect that the steps presented can optionally be incorporated in or otherwise used in conjunction with other routines. In this context, “start” indicates the beginning of the first step presented and may be preceded by other activities not specifically shown. Further, the “continue” indication reflects that the steps presented may be performed multiple times and/or may be succeeded by other activities not specifically shown. Further, while a flow diagram indicates a particular ordering of steps, other orderings are likewise possible provided that the principles of causality are maintained.

The present invention may have also been described, at least in part, in terms of one or more embodiments. An embodiment of the present invention is used herein to illustrate the present invention, an aspect thereof, a feature thereof, a concept thereof, and/or an example thereof. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process that embodies the present invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of the various embodiments of the present invention. A module includes a processing module, a functional block, hardware, and/or software stored on memory for performing one or more functions as may be described herein. Note that, if the module is implemented via hardware, the hardware may operate independently and/or in conjunction software and/or firmware. As used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of the present invention have been expressly described herein, other combinations of these features and functions are likewise possible. The present invention is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A method for execution by a dispersed storage and task (DST) execution unit that includes a processor, the method comprises: updating a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories; receiving at least one encoded data slice for storage by the DST execution unit; generating a plurality of scores corresponding to each of the plurality of memories, wherein each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories; selecting one of the plurality of memories based on the plurality of scores; and storing the at least one encoded data slice in the selected one of the plurality of memories.
 2. The method of claim 1, wherein the indication of the change of the memory capacity is generated based on interpreting an error message.
 3. The method of claim 1, further comprising performing a memory test on the plurality of memories; wherein the indication of the change of memory capacity is generated based on comparing a result of the memory test to a previous result corresponding to a previous memory test.
 4. The method of claim 1, wherein the indication of the change of the memory capacity is generated based on one of: a failure or removal of a memory block of the one of the plurality of memories.
 5. The method of claim 1, wherein the plurality of weighting factors are updated in response to an indication that the change in memory capacity is greater than a predefined threshold.
 6. The method of claim 1, wherein the selected one of the plurality of memories is determined based on the corresponding one of the plurality of memories with the highest corresponding score.
 7. The method of claim 1, wherein each of the plurality of scores is further generated based on an attribute of the received encoded slice.
 8. The method of claim 1, wherein the indication of a change in the memory capacity indicates a lowered memory capacity of the one of the plurality of memories, and wherein the plurality of weighting factors are updated by decreasing a weighting factor of the plurality of weighting factors corresponding to the one of the plurality of memories with the lowered memory capacity, and increasing remaining ones of the weighting factors of remaining memories of the plurality of memories.
 9. The method of claim 8, wherein the decrease of the weighting factor of the corresponding one of the plurality of memories with the lowered memory capacity is proportional to a degree of change in the memory capacity, and remaining ones of the plurality of weighting factors corresponding to the remaining memories are increased based on the decrease in the weighting factor of the one of the plurality of memories with the lowered memory capacity.
 10. The method of claim 1, wherein the plurality of weighting factors are updated in response to an indication that at least one second encoded data slice has been one of: written to or deleted from the one of the plurality of memories.
 11. A processing system of a dispersed storage and task (DST) execution unit comprises: at least one processor; a memory that stores operational instructions, that when executed by the at least one processor causes the processing system to: update a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories; receive at least one encoded data slice for storage by DST execution unit; generate a plurality of scores corresponding to each of the plurality of memories, wherein each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories; select one of the plurality of memories based on the plurality of scores; and store the at least one encoded data slice in the selected one of the plurality of memories.
 12. The processing system of claim 11, wherein the indication of the change of the memory capacity is generated based on interpreting an error message.
 13. The processing system of claim 11, wherein execution of the operational instructions by the at least one processor further causes the processing system to perform a memory test on the plurality of memories; wherein the indication of the change of memory capacity is generated based on comparing a result of the memory test to a previous result corresponding to a previous memory test.
 14. The processing system of claim 11, wherein the indication of the change of the memory capacity is generated based on one of: a failure or removal of a memory block of the one of the plurality of memories.
 15. The processing system of claim 11, wherein the plurality of weighting factors are updated in response to an indication that the change in memory capacity is greater than a predefined threshold.
 16. The processing system of claim 11, wherein the selected one of the plurality of memories is determined based on the corresponding one of the plurality of memories with the highest corresponding score.
 17. The processing system of claim 11, wherein the indication of a change in the memory capacity indicates a lowered memory capacity of the one of the plurality of memories, and wherein the plurality of weighting factors are updated by decreasing a weighting factor of the plurality of weighting factors corresponding to the one of the plurality of memories with the lowered memory capacity, and increasing remaining ones of the weighting factors of remaining memories of the plurality of memories.
 18. The processing system of claim 17, wherein the decrease of the weighting factor of the corresponding one of the plurality of memories with the lowered memory capacity is proportional to a degree of change in the memory capacity, and remaining ones of the plurality of weighting factors corresponding to the remaining memories are increased based on the decrease in the weighting factor of the one of the plurality of memories with the lowered memory capacity.
 19. The processing system of claim 11, wherein the plurality of weighting factors are updated in response to an indication that at least one second encoded data slice has been one of: written to or deleted from the one of the plurality of memories.
 20. A non-transitory computer readable storage medium comprises: at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to: update a plurality of weighting factors corresponding to each of a plurality of memories in response to an indication of a change in memory capacity of one of the plurality of memories; receive at least one encoded data slice for storage; generate a plurality of scores corresponding to each of the plurality of memories, wherein each of the plurality of scores is based on one of the plurality of weighting factors of a corresponding one of the plurality of memories; select one of the plurality of memories based on the plurality of scores; and store the at least one encoded data slice in the selected one of the plurality of memories. 